Noise-based gain adjustment and amplitude estimation system

ABSTRACT

Methods and systems for amplitude estimation and gain adjustment using noise as a reference are described. An example receiver can include an antenna and a front end amplifier coupled to the antenna. The receiver can also include a detector circuit coupled to the front end amplifier. The receiver can be configured to determine a power of a received signal at the antenna based on a gain of the receiver. The gain of the receiver can be determined based on a noise figure of the front end amplifier and a noise amplitude.

Embodiments relate generally to radio receivers, and more particularly,to methods and systems for signal amplitude estimation and system gainadjustment using noise as a reference.

Some receivers may estimate absolute signal amplitude based on anassumption that for a given configuration (e.g., operating settings),system gain would be constant from system to system. And althoughvariation in gain is known to exist, a nominal gain value is oftenchosen. Deviations from the nominal value can result in errors whenestimating absolute signal amplitude.

Embodiments were conceived in light of the above-mentioned problems andlimitations, among other things.

Some embodiments can include a receiver having an antenna, a front endamplifier coupled to the antenna, and a detector circuit coupled to thefront end amplifier. The receiver can be configured to measure signalamplitude at the detector, which can be used to infer received signalamplitude at the antenna based on a gain of the receiver system, basedon the following formula:

P _(D) =P _(S) +G ₁ +G ₂

where P_(D) is the measured signal amplitude at the detector, P_(S) isthe signal amplitude at the antenna, G₁ is the gain of the antenna andany circuitry up to but not including the front end amplifier and may beknown or can be determined by well known techniques, G₂ is the gain ofthe front end amplifier and subsequent circuitry up to the point ofmeasurement. G₂ may not be precisely known, but can be determined asdescribed below.

The receiver can include a programmable attenuator configured to adjustsystem gain level, G₂. The system gain level can be selected so as toset observed noise to a predetermined level.

The receiver gain, G₂, can be determined by measuring noise amplitude atthe detector in the absence of an input signal based on the formula:

P _(N) =G ₂ +NF+10 log₁₀(k)+10 log₁₀(T)+10 log₁₀(B)

where P_(N) is measured noise amplitude at the detector, NF is a systemnoise figure, k is Boltzmann's constant, T is absolute temperature and Bis bandwidth.

The receiver can include a plurality of physical channels. Each channelcan also include one or more corresponding programmable attenuators. Thereceiver can also include a max hold circuit configured to generate abiased estimation of noise power.

Some embodiments can include a method comprising providing a noiseestimation for a front end of a receiver, and placing the receiver intonoise mode. The method can also include measuring a noise amplitude at adetector subsequent to the receiver front end, and determining a systemgain based on the front end noise estimation and the noise amplitude.

The method can further include placing the receiver into a normalreceive mode, and receiving a signal at an antenna. The method caninclude determining a power level of the signal at the detector, anddetermining an estimated power level of the signal at the antenna basedon the system gain.

The method can include estimating a distance of the antenna to atransmitter of the signal based on the estimated power level of thesignal at the antenna. The absolute amplitude of the signal can beestimated based on a comparison of the signal amplitude at the detectorand estimate of the system gains, G₁ and G₂.

The method can also include comprising adjusting the system gain tomaximize instantaneous dynamic range. The method can further includeinjecting a high-level signal into the receiver so as to saturate thereceiver, and include estimating a maximum absolute signal level able tobe processed by the receiver.

The method can further include estimating a minimum absolute signallevel able to be processed by the receiver based on the noise amplitude.The method can include comprising removing bias from the noise amplitudemeasurement based on receiver behavior parameters including one or moreof integration time of a max hold circuit, IF bandwidth and videobandwidth. The method can also include setting a programmablethresholding circuit to achieve a predetermined false alarm probability.

Some embodiments can include a system having an antenna and a front endamplifier coupled to the antenna via a cable. The system can alsoinclude a detector circuit coupled to the front end amplifier and aprogrammable attenuator configured to set a system gain level.

The system can be configured to determine a power of a received signalat the antenna based on the system gain level. The system gain level canbe determined based on a noise amplitude of the system. Also, the systemgain level can be selected so as to set observed noise to apredetermined level.

The receiver can be configured to measure signal amplitude at thedetector, which can be used to infer received signal amplitude at theantenna based on a gain of the receiver system, based on the followingformula:

P _(D) =P _(S) +G ₁ +G ₂

where P_(D) is the measured signal amplitude at the detector, P_(S) isthe signal amplitude at the antenna, G₁ is the gain of the antenna andany circuitry up to but not including the front end amplifier, G₂ is thegain of the front end amplifier and subsequent circuitry up to the pointof measurement. G₁ and G₂ may not be precisely known.

The receiver can include a programmable attenuator configured to adjustsystem gain level, G₂. The system gain level can be selected so as toset observed noise to a predetermined level.

The receiver gain, G₂, can be determined by measuring noise amplitude atthe detector in the absence of an input signal based on the formula:

P _(N) =G ₂ +NF+10 log₁₀(k)+10 log₁₀(T)+10 log₁₀(B)

where P_(N) is measured noise amplitude at the detector, NF is a systemnoise figure, k is Boltzmann's constant, T is absolute temperature and Bis bandwidth.

The system can also include a plurality of physical channels each havingat least one corresponding programmable attenuator. The system canfurther include a max hold circuit configured to generate a biasedestimation of noise power. The system can also include a programmablethresholding circuit configured to be set so as to achieve apredetermined false alarm probability.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram of an example receiver system in accordance with atleast one embodiment.

FIG. 2 is a flowchart of an example method for amplitude estimation andgain adjustment using noise as a reference in accordance with at leastone embodiment.

FIG. 3 is a diagram of an example signal processing system in accordancewith at least one embodiment.

DETAILED DESCRIPTION

In general, the gain of a receiver can be determined based on noise inthe receiver system. The gain can then be used to estimate receivedsignal power at an antenna. Such signal power estimate can be useful forestimating the distance from a transmitter having a known power to areceiver. This kind of estimation may be useful in radar warningreceivers, electronic surveillance measures and the like. Embodimentsmay also be configured for use in audio applications.

FIG. 1 is a diagram of an example multi-channel receiver system 100. Thereceiver system 100 includes one or more antennas 102, cabling 104 toconnect each antenna 102 to a front-end amplifier (e.g., a low noiseamplifier). The receiver 100 system also includes a receiver/detectorcircuit 108 coupled to the low noise amplifier 106. FIG. 1 also showsthe sections of the system having gains G₁ and G₂.

In operation, the receiver 100 enters a calibration mode (or noise mode)and determines a system noise factor for the front-end. The noise factorcan be based on a theoretical formula or captured and analyzed data.Once the noise factor is determined, the receiver 100 can enter a “live”mode. Once in the “live” mode, the receiver 100 can use a fixed- orvariable-level threshold detector (not shown) to identify a signal abovenoise level.

A transmitter 110 may be at an unknown location and may have a known orestimated transmit power. The transmitter 110 can transmit a signal 112.The receiver system 100 can receive the signal 112 via antenna 102. Thereceiver system 100 can then use an estimate of the received signal 112power to determine an estimated location (or distance away from thereceiver 100) of the transmitter 110. The process of determining systemnoise is described below in connection with FIG. 2.

In some embodiments, the gain can be manually and/or automaticallyrecomputed as described herein, in response to a change in a systemconfiguration parameter such as gain, bandwidth, frequency tuning and/orthe like.

FIG. 2 is a flowchart of an example method for amplitude estimation andgain adjustment using noise as a reference in accordance with at leastone embodiment. Processing begins at 202, where a receiver is put intonoise mode. Noise mode can include switching off an antenna so that areceiver is receiving essentially a noise signal generated by thecircuitry. Processing continues to 204.

At 204, a noise level (or amplitude) for the receiver front end isdetermined. The noise level of the front end can be based on atheoretical estimate such as N=kTB, where N equals noise, k isBoltzmann's constant, T is absolute temperature and B is bandwidth. Thenoise level from the front end can also be provided, at least in part,by factory data. Processing continues to 206.

At 206, a power level (or amplitude) of the system noise signal ismeasured at the receiver/detector (e.g., 108). The receiver can includea programmable attenuator configured to adjust system gain level, G₂.The system gain level can be selected so as to set observed noise to apredetermined level. The receiver gain, G₂, can be determined bymeasuring noise amplitude at the detector in the absence of an inputsignal based on the formula:

P _(N) =G ₂ +NF+10 log₁₀(k)+10 log₁₀(T)+10 log₁₀(B)

where P_(N) is measured noise amplitude at the detector, NF is a systemnoise figure, k is Boltzmann's constant, T is absolute temperature and Bis bandwidth. Processing continues to 208.

At 208, the receiver is placed into operating mode (e.g., the antenna isopened up). Processing continues to 210.

At 210, a power level (or signal amplitude) is determined at thereceiver/detector. Processing continues to 212.

At 212, the power or amplitude of the signal received at the antenna isestimated using the gain computed in 206, which includes terms for noiseand bandwidth. Processing continues to 214.

Regarding steps 210 and 212, as discussed above, the receiver can beconfigured to measure signal amplitude at the detector, which can beused to infer received signal amplitude at the antenna based on a gainof the receiver system, based on the following formula:

P _(D) =P _(S) +G ₁ +G ₂

where P_(D) is the measured signal amplitude at the detector, P_(S) isthe signal amplitude at the antenna, G₁ is the gain of the antenna andany circuitry up to but not including the front end amplifier, G₂ is thegain of the front end amplifier and subsequent circuitry up to the pointof measurement. G₁ and G₂ may not be precisely known.

At 214, the distance from the receiver antenna to a transmitter isestimated based on the received power.

It will be appreciated that 202-214 may be repeated in whole or in partin order to accomplish a contemplated amplitude estimation and/or gainadjustment task using noise as a reference.

FIG. 3 is an example signal processing system 300 in accordance with atleast one embodiment. The signal processing system 300 includes aprocessor 302, operating system 304 (optional), memory 306 and I/Ointerface 308. The memory 306 can include an amplitude and gainestimation application 310.

In operation, the processor 302 may execute the application 310 storedin the memory 306. The application 310 can include software instructionsthat, when executed by the processor, cause the processor to performoperations for signal processing in accordance with the presentdisclosure (e.g., performing one or more of steps 202-214 describedabove).

The application program 312 can operate in conjunction with theoperating system 304.

It will be appreciated that the modules, processes, systems, andsections described above can be implemented in hardware, hardwareprogrammed by software, software instructions stored on a nontransitorycomputer readable medium or a combination of the above. A system asdescribed above, for example, can include a processor configured toexecute a sequence of programmed instructions stored on a nontransitorycomputer readable medium. For example, the processor can include, butnot be limited to, a signal processor, a programmable receiver, apersonal computer or workstation or other such computing system thatincludes a processor, microprocessor, microcontroller device, or iscomprised of control logic including integrated circuits such as, forexample, an Application Specific Integrated Circuit (ASIC). Theinstructions can be compiled from source code instructions provided inaccordance with a programming language such as Java, C, C++, C#.net,assembly or the like. The instructions can also comprise code and dataobjects provided in accordance with, for example, the Visual Basic™language, or another structured or object-oriented programming language.The sequence of programmed instructions, or programmable logic deviceconfiguration software, and data associated therewith can be stored in anontransitory computer-readable medium such as a computer memory orstorage device which may be any suitable memory apparatus, such as, butnot limited to ROM, PROM, EEPROM, RAM, flash memory, disk drive and thelike.

Furthermore, the modules, processes systems, and sections can beimplemented as a single processor or as a distributed processor.Further, it should be appreciated that the steps mentioned above may beperformed on a single or distributed processor (single and/ormulti-core, or cloud computing system). Also, the processes, systemcomponents, modules, and sub-modules described in the various figures ofand for embodiments above may be distributed across multiple computersor systems or may be co-located in a single processor or system. Examplestructural embodiment alternatives suitable for implementing themodules, sections, systems, means, or processes described herein areprovided below.

The modules, processors or systems described above can be implemented asa programmed general purpose computer, an electronic device programmedwith microcode, a hard-wired analog logic circuit, software stored on acomputer-readable medium or signal, an optical computing device, anetworked system of electronic and/or optical devices, a special purposecomputing device, an integrated circuit device, a semiconductor chip,and/or a software module or object stored on a computer-readable mediumor signal, for example.

Embodiments of the method and system (or their sub-components ormodules), may be implemented on a general-purpose computer, aspecial-purpose computer, a programmed microprocessor or microcontrollerand peripheral integrated circuit element, an ASIC or other integratedcircuit, a digital signal processor, a hardwired electronic or logiccircuit such as a discrete element circuit, a programmed logic circuitsuch as a PLD, PLA, FPGA, PAL, or the like. In general, any processorcapable of implementing the functions or steps described herein can beused to implement embodiments of the method, system, or a computerprogram product (software program stored on a nontransitory computerreadable medium).

Furthermore, embodiments of the disclosed method, system, and computerprogram product (or software instructions stored on a nontransitorycomputer readable medium) may be readily implemented, fully orpartially, in software using, for example, object or object-orientedsoftware development environments that provide portable source code thatcan be used on a variety of computer platforms. Alternatively,embodiments of the disclosed method, system, and computer programproduct can be implemented partially or fully in hardware using, forexample, standard logic circuits or a VLSI design. Other hardware orsoftware can be used to implement embodiments depending on the speedand/or efficiency requirements of the systems, the particular function,and/or particular software or hardware system, microprocessor, ormicrocomputer being utilized. Embodiments of the method, system, andcomputer program product can be implemented in hardware and/or softwareusing any known or later developed systems or structures, devices and/orsoftware by those of ordinary skill in the applicable art from thefunction description provided herein and with a general basic knowledgeof the electrical engineering and signal processing arts.

Moreover, embodiments of the disclosed method, system, and computerreadable media (or computer program product) can be implemented insoftware executed on a programmed general purpose computer, a specialpurpose computer, a microprocessor, or the like.

It is, therefore, apparent that there is provided, in accordance withthe various embodiments disclosed herein, methods, systems and computerreadable media for amplitude estimation and gain adjustment using noiseas a reference.

While the disclosed subject matter has been described in conjunctionwith a number of embodiments, it is evident that many alternatives,modifications and variations would be, or are, apparent to those ofordinary skill in the applicable arts. Accordingly, Applicant intends toembrace all such alternatives, modifications, equivalents and variationsthat are within the spirit and scope of the disclosed subject matter.

1-19. (canceled)
 20. A receiver comprising: an antenna; a front endamplifier coupled to the antenna; and a detector circuit coupled to thefront end amplifier, wherein the receiver is configured to determine apower of a received signal at the antenna based on a gain of thereceiver, and wherein the gain of the receiver (G₂) is determined basedon a noise figure of the front end amplifier and a noise amplitudemeasured by the detector circuit.
 21. The receiver of claim 20, furthercomprising a programmable attenuator configured to set system gainlevel.
 22. The receiver of claim 21, wherein the system gain level isselected based on a predetermined noise level.
 23. The receiver of claim20, wherein the gain of the receiver, G₂, is determined by measuring thenoise amplitude at the detector in an absence of an input signal. 24.The receiver of claim 23, wherein the gain of the receiver, G₂, isdetermined based on the measured noise amplitude at the detector, thesystem noise figure, Boltzmann's constant, an absolute temperature, anda bandwidth of the receiver.
 25. The receiver of claim 20, furthercomprising a plurality of physical channels each having at least onecorresponding programmable attenuator.
 26. The receiver of claim 20,further comprising a max hold circuit configured to generate a biasedestimation of noise power.
 27. The receiver of claim 20, wherein thereceiver is configured to estimate a distance of the antenna to atransmitter of the received signal based on the determined power of thereceived signal.
 28. A system comprising: an antenna; a front endamplifier coupled to the antenna via a cable; a detector circuit coupledto the front end amplifier; and a programmable attenuator configured toset a system gain level (G₂), wherein the system is configured todetermine a power of a received signal at the antenna based on thesystem gain level, and wherein the system gain level is determined basedon a noise amplitude of the system measured by the detector circuit anda system noise figure.
 29. The system of claim 28, wherein the systemgain level is selected based on a predetermined noise level.
 30. Thesystem of claim 28, wherein the system gain level, G₂, is determined bymeasuring the noise amplitude at the detector in an absence of an inputsignal.
 31. The system of claim 30, wherein the system gain level, G₂,is based on the measured noise amplitude at the detector, the systemnoise figure, Boltzmann's constant, absolute temperature, and bandwidth.32. The system of claim 28, further comprising a plurality of physicalchannels each having at least one corresponding programmable attenuator.33. The system of claim 28, further comprising a max hold circuitconfigured to generate a biased estimation of noise power.
 34. Thesystem of claim 28, further comprising a programmable thresholdingcircuit configured to be set so as to achieve a predetermined falsealarm probability.
 35. The system of claim 28, wherein the system isconfigured to estimate a distance of the antenna to a transmitter of thereceived signal based on the power of the received signal.